The present invention relates generally to tractor transmission lubrication and more particularly to lubricating and cooling the front differential in a tractor transmission.
In the past, the lubrication system for the front differential has been totally independent of the remainder of the transmission. The front differential was vented to atmosphere and provided with its own special lubricant with a common oil level in the differential and final drive spaces.
A large number of problems were recognized and accepted with this self-contained front differential lubrication system.
One of the major problems was that a high oil level had to be maintained in the final drive gears which accordingly means that the differential gears, which can operate with a low oil level, would have to churn through the high oil level and incur extremely high power losses.
Another major problem was that the oil turbulence in the front differential would naturally result in extensive heat buildup.
Another problem was that the oil turbulence causes a generally higher temperature operation of the front differential than in any other major component thus requiring a special oil to be used in the front differential. This oil is different from the oil used throughout the remainder of the tractor transmission and hydraulic system and must frequently be checked to assure that the proper oil level is maintained.
A consequence of the heavier weight oil and the single oil level lubrication was that oil would be centrifuged out of the internal differential gear parts at high speeds resulting in poor lubrication.
An additional problem was presented by the vent which can plug with dirt and cause a high pressure build-up of air in the front differential.
An additional problem which is incurred with front differentials having hydraulic differential lock is that the oil in the hydraulic system would be a different viscosity from that in the front differential and thus elaborate seals were required to prevent mixing of the two oils.